Fix PR28831 - Bad logic around CMAKE_OSX_SYSROOT and CMAKE_OSX_ARCHITECTURES.

See https://llvm.org/bugs/show_bug.cgi?id=28831 for more information about
the changes.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@280037 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CMakeLists.txt

@@ -105,9 +105,9 @@ if ( APPLE AND (LIBCXX_CXX_ABI_LIBNAME STREQUAL "libcxxabi" OR
       "-Wl,-unexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++unexp.exp"
       "/usr/lib/libSystem.B.dylib")
   else()
-    if ( ${CMAKE_OSX_SYSROOT} )
+    if (DEFINED CMAKE_OSX_SYSROOT)
       list(FIND ${CMAKE_OSX_ARCHITECTURES} "armv7" OSX_HAS_ARMV7)
-      if (OSX_HAS_ARMV7)
+      if (NOT OSX_HAS_ARMV7 EQUAL -1)
         set(OSX_RE_EXPORT_LINE
           "${CMAKE_OSX_SYSROOT}/usr/lib/libc++abi.dylib"
           "-Wl,-reexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++sjlj-abi.exp")